This invention relates to Micro Electromechanical Systems (MEMS) devices
Micro Electromechanical Systems (MEMS) devices, in particular, MEMS mirror arrays, are currently receiving a great deal of attention as the central component of high capacity optical switches for telecommunications applications. Such a switch can be made from a silicon chip which has formed thereon an array of tiny movable mirrors aligned with input and output fibers. In one type of switch, input beams are parallel to the major surface of the silicon wafer, and the path of any particular incoming beam can be diverted to one of several output fibers by activating a selected mirror in the array so that it is located in the path of the beam for reflection. (See, e.g., Lin et al, xe2x80x9cOn the Expandability of Free-Space Micromachined Optical Cross Connects,xe2x80x9d Journal of Lightwave Technology, vol. 18, pp 482-489 (April 2000) and Lin et al, xe2x80x9cFree-Space Micromachined Optical Switches for Optical Networking,xe2x80x9d IEEE Journal of Selected Topics in Quantum Electronics, vol. 5, pp. 4-9 (January/February 1999).) In another type of switch, the mirrors can be rotated in two axes simultaneously, the light is directed at the array at a near normal angle to the silicon, and each mirror is capable of directing a dedicated input beam to any one of the output fibers by an appropriate rotation of the selected mirror. (See, e.g., Hecht, xe2x80x9cAll Optical Networks Need All Optical Switches, Laser Focus World, pp 189-196 (May 2000).) MEMS devices can also be combined with a silicon optical bench device to provide a switching function for the optical bench device. (See, e.g., U.S. Pat. No. 5,995,688 issued to Aksyuk et al.)
The mirror array is currently formed on a silicon wafer which also includes conductors for applying a bias to the selected mirrors. Fabrication of the device tends to be complex and time-consuming since it usually involves, among other things, via etching of the wafer and conductor back-filling of the vias in order to provide the conductor pattern and package the device.
It is desirable, therefore, to provide a MEMS device and method of fabrication which is simplified yet robust and can accommodate the need for conductor definition in large arrays.
The invention in accordance with one aspect is a device comprising an array of electrostatically activated members (e.g., mirrors) formed in a layer comprising silicon, and a substrate comprising a ceramic material and including conductors formed on a major surface of the substrate and in via holes formed in the substrate, the conductors being positioned so as to selectively operate the array of members.
The invention in accordance with another aspect is a method of forming a device comprising forming an array of electrostatically activated members (e.g., mirrors) in a layer of silicon, and mounting said silicon layer over a substrate comprising a ceramic material which includes conductors formed on a major surface of the substrate and in via holes formed in the substrate. The silicon layer is mounted so as to position the members with respect to the conductors to permit selective operation of the members.